Loot the Essences of Ice from the Brittle Revenants, then head to the Fjorn's Anvil area and throw the essences at Smoldering Scraps on the ground.

Frozen Ice Scraps can be looted by any player, not just the one who froze them, which means that they are vulnerable to ninjas (this also means that a player with excess Essence of Ice can use them to freeze scraps for other players).